Optoelectronic sensor

ABSTRACT

In an embodiment an optoelectronic sensor includes a radiation-emitting semiconductor region, a radiation-detecting semiconductor region, a first polarization filter arranged above the radiation-emitting semiconductor region and including a first polarization direction and a second polarization filter arranged above the radiation-detecting semiconductor region and including a second polarization direction, wherein the first polarization direction and the second polarization direction are perpendicular to each other, wherein a radiation-reflecting or radiation-absorbing layer is arranged on side flanks of the radiation-emitting semiconductor region and/or the radiation-detecting semiconductor region and/or the first polarization filter and/or the second polarization filter.

This patent application is a national phase filing under section 371 ofPCT/EP2019/077195, filed Oct. 8, 2019, which claims the priority ofGerman patent application 102018125050.9, filed Oct. 10, 2018, each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This application relates to an optoelectronic sensor, in particular anoptoelectronic sensor for measuring a vital parameter in a wearabledevice.

BACKGROUND

Monitoring of vital parameters by an optoelectronic sensor in a wearabledevice, for example in a sports watch, requires a particularly compactsensor with high sensitivity.

SUMMARY OF THE INVENTION

Embodiments provide an optoelectronic sensor that has a compact designand a high sensitivity.

According to at least one embodiment, the optoelectronic sensorcomprises a radiation-emitting semiconductor region and aradiation-detecting semiconductor region. The radiation-emittingsemiconductor region comprises, in particular, an active layer suitablefor emitting radiation. The active layer can be formed, for example, asa pn junction, a double heterostructure, a single quantum well structureor a multiple quantum well structure. The term quantum well structureincludes any structure in which charge carriers undergo quantization oftheir energy states by confinement. In particular, the term quantum wellstructure does not contain any indication of the dimensionality of thequantization. Thus, it includes inter alia quantum wells, quantum wires,and quantum dots, and any combination of these structures.

In particular, the radiation-detecting semiconductor region comprises anactive layer suitable for detecting radiation, such as a photodiode orother semiconductor layer sequence suitable for detecting radiation.

According to at least one embodiment, the optoelectronic sensorcomprises a first polarization filter arranged above theradiation-emitting semiconductor region and a second polarization filterarranged above the radiation-detecting semiconductor region. Inparticular, the first polarization filter may be arranged directly on aradiation exit surface of the radiation-emitting semiconductor region.Similarly, the second polarization filter may be directly arranged onthe radiation entrance surface of the radiation-detecting semiconductorregion. Arranging the polarization filters directly on the semiconductorregions, for example in the form of a layer or a layer sequence,advantageously contributes to a compact structure of the optoelectronicsensor.

The first polarization filter comprises a first polarization directionand the second polarization filter comprises a second polarizationdirection. Here, the first polarization direction is different from thesecond polarization direction, in particular, the first polarizationdirection and the second polarization direction are perpendicular toeach other. For example, the first polarization filter arranged abovethe radiation-emitting semiconductor region generates linearly polarizedradiation having the first polarization direction, and the secondpolarization filter arranged above the radiation-detecting semiconductorregion generates linearly polarized radiation having a secondpolarization direction that is perpendicular to the first polarizationdirection. In other words, the first and second polarization filtersform crossed polarizers.

By the first and second polarization filters comprising polarizationdirections oriented perpendicular to each other, it is advantageouslyachieved that the radiation emitted from the radiation-emittingsemiconductor region exits the optoelectronic sensor with a polarizationdirection for which the second polarization filter above theradiation-detecting semiconductor region is substantiallynontransmissive.

In particular, the radiation emitted from the radiation-detectingsemiconductor region is provided as excitation light for measuring avital parameter. The emitted radiation may be at least partiallyabsorbed and/or reflected by a body region, such as tissue or bloodvessels. The radiation-detecting semiconductor region is particularlyprovided for detecting the radiation emitted from the body region as aresult of the excitation. In particular, the detected radiation may beused to detect one or more vital signs such as blood pressure and/orheart rate. The detected radiation typically comprises lower energyradiation, i.e., radiation of a longer wavelength. Furthermore, theradiation to be detected typically comprises very low intensity comparedto the intensity of the excitation light. Due to the fact that theexcitation light generated by the radiation-emitting semiconductorregion is substantially not transmitted by the second polarizationfilter because of its polarization direction, the excitation light isadvantageously separated from the radiation to be detected from the bodyregion before reaching the radiation-detecting semiconductor region.

Therefore, the light emitted from the radiation-emitting semiconductorregion contributes very little to the signal light detected by theradiation-detecting semiconductor region. In this way, a highsensitivity of the optoelectronic sensor is advantageously achieved.

According to at least one embodiment of the optoelectronic sensor, theradiation-detecting semiconductor region is arranged laterally next tothe radiation-emitting semiconductor region. In this way, the spacerequired for the optoelectronic sensor is kept small.

According to at least one embodiment of the optoelectronic sensor, theradiation exit surface of the radiation-emitting semiconductor regionand the radiation entrance surface of the radiation-detectingsemiconductor region are arranged parallel to each other.

In particular, the radiation-emitting semiconductor region and theradiation-detecting semiconductor region are arranged such that a mainemission direction of the radiation-emitting semiconductor region and amain incidence direction of the radiation-detecting semiconductor regionare substantially anti-parallel to each other.

According to at least one embodiment of the optoelectronic sensor, theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region are arranged on a common carrier. The commoncarrier may comprise, for example, electrical contacts for contactingthe radiation-emitting semiconductor region and the radiation-detectingsemiconductor region.

According to at least one embodiment of the optoelectronic sensor, theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region are monolithically integrated. “Monolithicallyintegrated” means, in particular, that the radiation-emittingsemiconductor region and the radiation-detecting semiconductor regioncomprise a common growth substrate. In particular, theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region may be epitaxially grown on the common growthsubstrate. It is possible that the radiation-emitting semiconductorregion and the radiation-detecting semiconductor region comprise, atleast in some regions, semiconductor layers grown in the same epitaxialgrowth process. The radiation-emitting semiconductor region and/or theradiation-detecting semiconductor region may comprise, in particular, amesa structure. Thus, the lateral extent of the semiconductor layersequence is smaller than the lateral extent of a supporting substratesuch as the growth substrate. The mesa structure may be fabricated by aphotolithographic process in which the semiconductor layer sequence ispartially ablated to pattern it to a desired shape and size.

According to at least one embodiment of the optoelectronic sensor, adistance between the radiation-emitting semiconductor region and theradiation-detecting semiconductor region is not more than 150 μm. Here,the “distance” means the shortest distance between theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region, i.e., the width of the gap between theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region. Preferably, the distance is at least 20 μm toreduce optical crosstalk. Thus, the distance between theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region is preferably between 20 μm and 150 μm.

According to at least one embodiment of the optoelectronic sensor, aradiation-reflecting or radiation-absorbing layer is applied to sideflanks of the radiation-emitting semiconductor region and/or theradiation-detecting semiconductor region. Preferably, both the sideflanks of the radiation-emitting semiconductor region and the sideflanks of the radiation-detecting semiconductor region are covered withthe radiation-reflecting or radiation-absorbing layer. In this way,optical crosstalk between the radiation-emitting semiconductor regionand the radiation-detecting semiconductor region can be further reduced.The radiation-reflecting or radiation-absorbing layer is preferably adielectric layer or layer sequence. Alternatively or additionally, theside flanks of the first polarization filter and/or the side flanks ofthe second polarization filter may be covered by theradiation-reflecting or radiation-absorbing layer.

According to at least one embodiment of the optoelectronic sensor, thefirst polarization filter and/or the second polarization filter is anabsorbing polarization filter. In an absorbing polarization filter,light with the pass polarization direction is transmitted and otherpolarization directions are absorbed within the polarization filter. Inthis embodiment, the first and/or second polarization filter maycomprise, for example, herapathite.

According to at least one embodiment of the optoelectronic sensor, thefirst polarization filter and/or the second polarization filter is areflective polarization filter.

In a reflective polarization filter, light with the pass polarizationdirection is transmitted and other polarization directions arereflected. In this embodiment, the first and/or second polarizationfilter may comprise, for example, a dielectric layer sequence.

According to at least one embodiment of the optoelectronic sensor, theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region are surrounded in the lateral direction by aplastic molding compound comprising, for example, silicone or epoxyresin. The plastic molding compound can be applied by injection molding,transfer molding, or compression molding, for example. The plasticmolding compound is advantageously opaque, i.e., in particular, nottransparent to the emitted radiation. Preferably, the plastic moldingcompound contains radiation-absorbing and/or radiation-reflectingparticles. In this way, the crosstalk between the radiation-emittingsemiconductor region and the radiation-detecting semiconductor regioncan be further reduced. Alternatively or additionally, the side flanksof the first polarization filter and/or the side flanks of the secondpolarization filter may be covered by the plastic molding compound.

According to at least one embodiment, the optoelectronic component is asurface mounted device (SMD). In this embodiment, in particular theelectrical contacts are arranged on a back side facing away from theradiation exit surface and radiation entrance surface, so that thecomponent can be mounted on the back side, for example on a printedcircuit board. In this case, the front side of the optoelectronic sensoris advantageously free of electrical leads such as bonding wires, sothat absorption of the emitted light or the light to be detected byelectrical leads is avoided.

According to at least one embodiment of the optoelectronic sensor, theradiation-emitting semiconductor region is suitable for emittinginfrared radiation and the radiation-detecting semiconductor region issuitable for detecting infrared radiation. In this embodiment, theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region may be based on an arsenide compound semiconductor,for example. “Based on an arsenide compound semiconductor” in thepresent context means that the active epitaxial layer sequence, or atleast one layer thereof, comprises an arsenide compound semiconductormaterial, preferably Al_(n)Ga_(m)In_(1-n-m)As, wherein 0≤n≤1, 0≤m≤1 andn+m≤1. This material need not necessarily comprise a mathematicallyexact composition according to the above formula. Rather, it maycomprise one or more dopants as well as additional constituents. For thesake of simplicity, however, the above formula includes only theessential constituents of the crystal lattice (Al, Ga, In, As), even ifthese may be partially replaced by small amounts of other substances.Alternatively, however, it is also possible for the radiation-emittingsemiconductor region and/or the radiation-detecting semiconductor regionto be based on a different semiconductor material, in particular on aIII-V semiconductor material.

The optoelectronic sensor may in particular be configured to measure atleast one vital parameter. A vital parameter is a measure that reflectsa basic function of the human body. Such a vital parameter may be, forexample, the heart rate or the blood pressure or the oxygen content inthe blood.

According to at least one embodiment, the optoelectronic sensor is partof a wearable device, in particular a wearable device for measuring avital parameter such as, for example, a sports watch or a fitnesswristband. The compact design of the optoelectronic sensor isparticularly advantageous for the integration of the optoelectronicsensor into such a device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below by means of exemplaryembodiments in connection with FIGS. 1 to 6 .

FIG. 1 shows a schematic representation of a cross-section through anoptoelectronic sensor according to a first exemplary embodiment;

FIG. 2 shows a schematic representation of a cross-section through anoptoelectronic sensor according to a further exemplary embodiment;

FIG. 3 shows a schematic representation of a cross-section through anoptoelectronic sensor according to a further exemplary embodiment;

FIG. 4 shows a schematic representation of the beam path in an exemplaryembodiment of the optoelectronic sensor;

FIG. 5 shows a schematic representation of the beam path in anoptoelectronic sensor with a small distance between theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region; and

FIG. 6 shows a schematic representation of the beam path in anoptoelectronic sensor with a large distance between theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region.

Components that are the same or have the same effect are each given thesame reference signs in the figures. The components shown as well as theproportions of the components among each other are not to be regarded astrue to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 schematically shows a first exemplary embodiment of theoptoelectronic sensor in cross-section. The optoelectronic sensor 1comprises a radiation-emitting semiconductor region 2 and aradiation-detecting semiconductor region 3. The radiation-emittingsemiconductor region 2 and the radiation-detecting semiconductor region3 are each formed by a semiconductor layer sequence whose individuallayers are not shown here.

For example, the radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 may each comprise asemiconductor layer sequence based on a III-V semiconductor material,such as a semiconductor layer sequence based on an arsenide compoundsemiconductor material. In particular, the radiation-emittingsemiconductor region 2 may comprise a light-emitting diode layersequence. The radiation-detecting semiconductor region 3 may be aphotodiode, for example.

The radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 are arranged laterallyadjacent to each other such that a radiation exit surface of theradiation-emitting semiconductor region and a radiation entrance surfaceof the radiation-detecting semiconductor region are arranged parallel toeach other, in particular in a plane.

The radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 are arranged on a commoncarrier 6. The common carrier 6 may in particular be a common growthsubstrate. In other words, the radiation-emitting semiconductor region 2and the radiation-detecting semiconductor region 3 are monolithicallyintegrated. In particular, the semiconductor layer sequences of theradiation-emitting semiconductor region 2 and the radiation-detectingsemiconductor region 3 may be epitaxially grown on the common growthsubstrate. The radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 comprise, in particular, amesa structure that can be produced, for example, by an etching process.

Alternatively, it is also possible that the radiation-emittingsemiconductor region 2 and the radiation-detecting semiconductor region3 are separately fabricated semiconductor chips that are connected tothe common carrier 6 by means of a bonding layer such as a solder layer.In this embodiment, the radiation-emitting semiconductor region 2 andthe radiation-detecting semiconductor region 3 may be, in particular,so-called thin-film semiconductor bodies. In the production of athin-film semiconductor body, a functional semiconductor layer sequence,which in particular comprises the active layer, is first epitaxiallygrown on a growth substrate, then the carrier 6 is applied on thesurface of the semiconductor layer sequence opposite the growthsubstrate, and subsequently the growth substrate is separated. Since thegrowth substrates used for nitride compound semiconductors, for exampleSiC, sapphire or GaN, are comparatively expensive, this method offersthe advantage that the growth substrate can be recycled. The detachmentof a growth substrate made of sapphire from a semiconductor layersequence made of a nitride compound semiconductor can, for example, becarried out using a laser lift-off method.

The common carrier 6 comprises electrodes 7 on the back side forelectrically contacting the radiation-emitting semiconductor region 2and the radiation-detecting semiconductor region 3. The electricalconnections between the electrodes 7 and the radiation-emittingsemiconductor region 2 and the radiation-detecting semiconductor region3 are not shown in detail here for convenience. It is possible, forexample, that these connections are realized by way of vias through thecarrier 6. The common carrier 6 may be, for example, a silicon substrateor a glass substrate.

The optoelectronic sensor 1 is in particular a surface mountablecomponent. In particular, the optoelectronic sensor can be mounted on aprinted circuit board by means of electrodes 7 arranged on the back sideof the carrier 6. The optoelectronic sensor 1 can be connected at theelectrodes in particular to a control unit which is configured tocontrol the optoelectronic sensor and to evaluate the signal.

In the case of the optoelectronic sensor 1, a first polarization filter4 is arranged above the radiation-emitting semiconductor region 2. Inthe exemplary embodiment, the first polarization filter 4 is aradiation-absorbing polarization filter, which transmits radiation ofonly one polarization direction P1 from the emitted radiation andabsorbs other polarization directions. The first polarization filter 4can generate, in particular, linearly polarized radiation with thepolarization direction P1 from the emitted radiation. For example, thefirst polarization direction P1 is oriented parallel to the drawingplane.

Furthermore, a second polarization filter 5 is arranged above theradiation-detecting semiconductor region 3. In the exemplary embodiment,the second polarization filter 5 is a radiation-absorbing polarizationfilter which only transmits radiation of a second polarization directionP2 and absorbs other polarization directions. The second polarizationfilter 5 may comprise, for example, a transmission direction forlinearly polarized radiation with the polarization direction P2. Thesecond polarization direction P2 is oriented perpendicular to thedrawing plane, for example.

The first polarization filter 4 is advantageously arranged directly onthe radiation-emitting semiconductor region 2, and the secondpolarization filter 5 is advantageously arranged directly on theradiation-detecting semiconductor region 3. The first polarizationfilter 4 and the second polarization filter 5 may be, for example,polarizing crystal platelets attached to the radiation-emittingsemiconductor region 2 and to the radiation-detecting semiconductorregion 3 by means of a bonding layer such as an adhesive.

The first polarization filter 4 and/or the second polarization filter 5may comprise, for example, herapathite.

The polarization direction P2 of the second polarization filter 5 isperpendicular to the polarization direction P1 of the first polarizationfilter 4, so the polarization directions P1 and P2 are crossed. In thisway, it is advantageously achieved that radiation emitted from theradiation-emitting semiconductor region 2 which has passed the firstpolarization filter 4 is not transmitted by the polarization filter 5above the radiation-detecting semiconductor region 3. In this way, theradiation-detecting semiconductor region 3 is shielded from the emittedradiation to the greatest extent possible. In other words, crosstalkbetween the radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 is reduced. In this way, thesensitivity of the radiation-detecting semiconductor region 3 to asignal radiation, which may be unpolarized in particular, isadvantageously increased compared to the sensitivity to the emittedradiation. In particular, the signal-to-noise ratio of the detectorsignal is improved in this way.

The radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 are laterally surrounded by aplastic molding compound 9. The plastic molding compound 9 isadvantageously opaque. In the exemplary embodiment, the plastic moldingcompound 9 is an opaque plastic molding compound that laterallysurrounds the radiation-emitting semiconductor region 2, the firstpolarization filter 4, the radiation-detecting semiconductor region 3,the second polarization filter 5, and the common carrier 6. Inparticular, the opaque plastic molding compound 9 may comprise a matrixmaterial having radiation-reflecting or radiation-absorbing particlesembedded therein. The matrix material may be, for example, a silicone oran epoxy resin, and the particles may be, for example, TiO₂ particles.The opaque plastic molding compound 9 may be applied, for example, byinjection molding, transfer molding, or compression molding. On the onehand, the plastic molding compound 9 serves to protect theoptoelectronic sensor 1 from external influences, for example to protectit from mechanical damage, dirt or moisture. In addition, the fact thatthe plastic molding compound 9 is opaque further reduces crosstalkbetween the radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3.

FIG. 2 illustrates a second exemplary embodiment of the optoelectronicsensor 1. The structure of the optoelectronic sensor 1 is substantiallythe same as that of the first exemplary embodiment. One difference fromthe first exemplary embodiment is that the first polarization filter 4and the second polarization filter 5 are designed as reflectivepolarization filters. The first polarization filter 4, which is arrangedon the radiation-emitting semiconductor region 2, is designed totransmit portions of radiation emitted with a first polarizationdirection P1 and to reflect back other portions of radiation.

In an analogous manner, the second polarization filter 5, which isarranged on the radiation-detecting semiconductor region 3, can also bedesigned as a reflective polarization filter. In this case, theradiation-detecting polarization filter 5 is configured to transmitportions of radiation of an incident signal light having the secondpolarization direction P2 and reflect back other portions of radiation.

The first polarization filter 4 and the second polarization filter 5 maycomprise a polarizing layer or layer sequence, in particular adielectric layer sequence. In particular, the first polarization filter4 and the second polarization filter 5 may be dielectric interferencelayer systems.

The reflective property of the first polarization filter 4 and/or thesecond polarization filter 5 has the advantage of enabling so-calledlight recycling. This means that, for example, radiation which hasentered the radiation-detecting semiconductor region 3 can be reflectedonce or several times between the reflective polarization filter 5 andthe back side of the radiation-detecting semiconductor region 3 facingthe carrier 6, until finally absorption takes place in thelight-sensitive active layer of the radiation-detecting semiconductorregion 3. Such radiation, which has not yet been absorbed after passingthrough the active layer once, is thus not lost, but can still beabsorbed after being reflected once or several times, thus contributingto the detector signal.

In an analogous manner, for example, photons which have not yet beentransmitted when first hitting the reflective polarization filter 4 ofthe radiation-emitting semiconductor region 2 may possibly betransmitted after being reflected once or several times in theradiation-emitting semiconductor region 2 and thus contribute to theemitted radiation.

A further difference between the second exemplary embodiment accordingto FIG. 2 and the first exemplary embodiment is that side flanks of theradiation-emitting semiconductor region 2 and the radiation-detectingsemiconductor region 3 are each provided with a radiation-reflecting orradiation-absorbing layer 8. In particular, the facing side flanks ofthe radiation-emitting semiconductor region and the radiation-detectingsemiconductor region 3 may be provided with the radiation-reflecting orradiation-absorbing layer 8. In addition, it is also possible that theside flanks of the radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 facing away from each otherare also covered with the radiation-absorbing layer 8. In particular,the radiation-reflecting or radiation-absorbing layer 8 may also coverthe side flanks of the first polarization filter 4 and the secondpolarization filter 5. The radiation-reflecting or radiation-absorbinglayer 8 further reduces crosstalk between the radiation-emittingsemiconductor region 2 and the radiation-detecting semiconductor region3.

FIG. 3 illustrates a third exemplary embodiment of the optoelectronicsensor 1. The third exemplary embodiment differs from the firstexemplary embodiment in that the radiation-emitting semiconductor region2 and the radiation-detecting semiconductor region 3 do not comprise acommon carrier 6, but separate carriers. Rather, in this exemplaryembodiment, the radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 are each part of a separatesemiconductor chip. Nevertheless, the radiation-emitting semiconductorregion 2 and the radiation-detecting semiconductor region 3 are alsoarranged next to each other at a small distance in this exemplaryembodiment, preferably at a distance of at least 20 μm and at most 150μm. The two semiconductor chips each comprise electrodes on the backside, so that advantageously both semiconductor chips arranged side byside are each surface-mountable semiconductor chips.

The radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 are surrounded by aradiation-nontransmissive plastic molding compound 9, as in the previousexamples. Advantageously, the plastic molding compound 9 is a plasticmolding compound that connects the two adjacent semiconductor chipstogether to form a one-piece optoelectronic sensor 1. In particular, thespace between the two adjacent semiconductor chips may be filled by theplastic molding compound 9. On the one hand, the plastic moldingcompound 9 represents the connecting member between the twosemiconductor chips. Furthermore, the plastic molding compound 9 isadvantageously opaque, so that optical crosstalk between theradiation-emitting semiconductor region 2 and the radiation-detectingsemiconductor region 3 is reduced. With regard to further possibleembodiments and the advantages resulting therefrom, the third exemplaryembodiment otherwise corresponds to the first exemplary embodiment.

FIG. 4 schematically illustrates a cross-section through anoptoelectronic sensor 1 in an application intended for theoptoelectronic sensor 1. The optoelectronic sensor 1 is configured as inthe first exemplary embodiment. Alternatively, however, it would also bepossible for the optoelectronic sensor 1 to be configured, for example,as in one of the exemplary embodiments of FIG. 2 or 3 . In a method ofoperating the optoelectronic sensor 1, the radiation-emittingsemiconductor region 2 emits radiation 10 in a main radiation directionthat is perpendicular to a main surface of the optoelectronic sensor 1.The emitted radiation 10 passes through the first polarization filter 4and is then advantageously linearly polarized.

The emitted radiation 10 can be absorbed as excitation light by anobject 11, where it can excite the emission of a signal radiation 12, apart of which is detected by the radiation-detecting semiconductorregion 3.

The signal radiation 12 reemitted after absorption typically comprises alower energy and thus a longer wavelength than the emitted radiation 10.The object 11 may be, for example, human tissue. It is also possiblethat the object is liquid or gaseous, for example a drop of sweat or agas excreted by the body can be examined.

FIG. 5 schematically shows the beam path in an optoelectronic sensor 1with a small distance between the radiation-emitting semiconductorregion and the radiation-detecting semiconductor region. The smalldistance is achieved in particular by arranging the radiation-emittingsemiconductor region 2 and the radiation-detecting semiconductor region3 next to each other on a common carrier 6, wherein the distance isadvantageously not more than 150 μm, in particular between 20 μm and 150μm. The emitted radiation 10 impinges on the object 11 at differentangles Θ. Similarly, the signal radiation 12 also impinges on theradiation-detecting semiconductor region 3 at different angles Θ. Theradiation characteristic of the emitted radiation 10 can, for example,approximately correspond to the beam characteristic of a Lambertradiator. In this case, the radiant intensity Ie of the emitted light isat least approximately proportional to the cosine of the angle Θ,wherein Θ=0° denotes the main radiation direction, thus I_(e)(Θ)=I_(o)cos Θ holds. Here, I_(e)(Θ) is the radiant intensity at angle Θ to themain radiation direction and Io is the radiant intensity present in themain radiation direction (Θ=0°).

The radiant energy A1 incident on the object under examination isproportional to the integral of the radiant intensity I_(e)(Θ) over theangles Θ at which the radiation strikes the object. Since, at leastapproximately, I_(e)(Θ)=I_(o) cos Θ applies, the smaller the angles Θrelative to the main radiation direction, the greater the radiantintensity.

For comparison, FIG. 6 schematically shows the beam path in anoptoelectronic sensor 1 with a greater distance between theradiation-emitting semiconductor region 2 and the radiation-detecting 3semiconductor region. In this example, the greater distance is based inparticular on the fact that the radiation-emitting semiconductor region2 and the radiation-detecting semiconductor region 3 are separatesemiconductor chips that are not arranged directly next to each other ona common carrier. In this case, the angles Θ relative to the mainradiation direction are larger than in the example of FIG. 5 , andtherefore the radiant energy A2 incident on the object under examinationis smaller than in the example of FIG. 5 . Thus, it can be seen thatarranging the radiation-emitting semiconductor region 2 and theradiation-detecting semiconductor region 3 side by side on a commoncarrier as shown in FIG. 5 is more advantageous.

The invention is not limited by the description based on the exemplaryembodiments. Rather, the invention encompasses any new feature as wellas any combination of features, which in particular includes anycombination of features in the claims, even if that feature orcombination itself is not explicitly specified in the claims orexemplary embodiments.

The invention claimed is:
 1. An optoelectronic sensor comprising: aradiation-emitting semiconductor region; a radiation-detectingsemiconductor region, wherein the radiation-emitting semiconductorregion and the radiation-detecting semiconductor region aremonolithically integrated and arranged on a common growth substrate; afirst polarization filter arranged above the radiation-emittingsemiconductor region and comprising a first polarization direction; asecond polarization filter arranged above the radiation-detectingsemiconductor region and comprising a second polarization direction,wherein the first polarization direction and the second polarizationdirection are perpendicular to each other; and a radiation-reflecting orradiation-absorbing layer applied to side flanks of theradiation-emitting semiconductor region and/or the radiation-detectingsemiconductor region and/or the first polarization filter and/or thesecond polarization filter.
 2. The optoelectronic sensor according toclaim 1, wherein the radiation-detecting semiconductor region isarranged laterally adjacent to the radiation-emitting semiconductorregion.
 3. The optoelectronic sensor according to claim 1, wherein theradiation-emitting semiconductor region and the radiation-detectingsemiconductor region are arranged on a common carrier.
 4. Theoptoelectronic sensor according to claim 1, wherein a distance betweenthe radiation-emitting semiconductor region and the radiation-detectingsemiconductor region is less than 150 μm.
 5. The optoelectronic sensoraccording to claim 1, wherein the first polarization filter and/or thesecond polarization filter is an absorbing polarization filter.
 6. Theoptoelectronic sensor according to claim 1, wherein the firstpolarization filter and/or the second polarization filter is areflective polarization filter.
 7. The optoelectronic sensor accordingto claim 1, wherein the radiation-emitting semiconductor region and theradiation-detecting semiconductor region are surrounded in a lateraldirection by a plastic molding compound.
 8. The optoelectronic sensoraccording to claim 1, wherein the first polarization filter and/or thesecond polarization filter are surrounded in a lateral direction by aplastic molding compound.
 9. The optoelectronic sensor according toclaim 7, wherein the plastic molding compound containsradiation-absorbing or radiation-reflecting particles.
 10. Theoptoelectronic sensor according to claim 1, wherein the optoelectronicsensor is a surface mounted device.
 11. The optoelectronic sensoraccording to claim 1, wherein the radiation-emitting semiconductorregion is configured to emit infrared radiation and theradiation-detecting semiconductor region is configured to detectinfrared radiation.
 12. The optoelectronic sensor according to claim 1,wherein the optoelectronic sensor is configured to measure at least onevital parameter.
 13. The optoelectronic sensor according to claim 1,wherein the optoelectronic sensor is a component of a wearable device.14. The optoelectronic sensor according to claim 1, wherein theradiation-reflecting or radiation-absorbing layer directly adjoins theradiation-emitting semiconductor region, the radiation-detectingsemiconductor region, the first polarization filter and the secondpolarization filter.